Extreme pressure lubricant



United States Patent EXTREME PRESSURE LUBRICANT Morton Fainman, Chicago, Ill., assignor to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Application November 29, 1954 Serial No. 471,877

1 Claim. (Cl. 252-3345) This invention relates to lead sulfurized tall oil, a composition having value as an extreme pressure lubricant, and its use in lubricating oil compositions to impart extreme pressure lubricating properties.

Many compositions containing lead and sulfur have been proposed as extreme pressure lubricating additives. Of these, the most commonly used are sulfurized sperm oil and lead naphthenate. Both are relatively expensive, particularly sulfurized sperm oil, and both, in times of unsettled world conditions, tend to be in short supply. I have discovered that lead sulfurized tall oil has value as an extreme pressure lubricating additive. When it is incorporated in a mineral oil base, it imparts improved extreme pressure lubricating properties. For example, when tested under the conditions of the Timken wear and lubricating test procedure (described in the Journal of the Institute of Petroleum, vol. 25, pp. 738-742, 1939), the resulting oil shows markedly increased load bearing capacity. Thus, lead sulfurized tall oil is not only a complete replacement for sulfurized sperm oil in lubricating compositions formulated for use under high load and/ or rate of shear application, e. g., for use as gear oils, but it provides lead in suitably soluble form at the same time, permitting replacement of lead naphthenate. I have found that the use of lead sulfurized tall oil results in products of satisfactory oxidation stability whereas corresponding lead soaps of unsulfurized tall oil result in products of unsatisfactory oxidation stability.

Lead sulfurized tall oil may be prepared by direct sulfurization of tall oil followed by formation of a lead soap. The sulfurization reaction may be conducted by heating distilled tall oil with sulfur at a temperature of about 250 F. to 350 F. The amount of sulfur is preferably in excess of the stoichiometric amount based on the unsaturation of the tall oil feed. The reaction mixture should be heated for a period of several hours until the sulfurization reaction has been completed. A typical product contains about 9 to 10% by weight of sulfur. Several procedures are available for converting the sulfurized tall oil to a lead soap, for example, as by double decomposition of a sodium soap of the sulfurized tall oil with a lead salt such as lead acetate. I have found however, that reaction of the sulfurized tall oil with lead oxide in the presence of water and a water miscible alcohol type solvent such as a Cellosolve or a Carbitol has special advantages. Higher yields without loss of sulfur as lead sulfide are obtained while avoiding the more laborious procedure involved in preparation by double decomposition.

Although lead sulfurized tallate is usually insoluble in a predominantly parafiin type oil, it is soluble to the extent of about to percent in isoparafiinic oils of the type derived from Winkler crude oil, for example. The lead sulfurized tallate also is soluble to the extent of about 20 percent or more in oils that are rich in aromatics, for example, hydroformer bottoms and lubrieating oil extracts such as those produced as an incident to solvent refining of lubricating oils with a selective solvent such as phenol or dichloro-diethylether. Paraflin type oils may be used as a base oil with lead sulfurized tallate when solubility imposes an undesirable limit on the concentration of tallate byblendingithe paraffinic oil, such as a Mid-Continent solvent refined lubricating oil fraction, with aromatics or aromatic rich oils to the extent desired, e. g. about 25 to percent. Aviscosity range of about 500 to 2000, advantageously 600-1000, SSU at F. for the base oil is in general suitable.

In formulating lubricating compositions havingextreme pressure properties, the lead sulfurized tall oil may be used in a proportion ranging from about 1 or 2 percent to the limit of solubility, usually about 20-25 percent by weight. A concentration of about 10 to 15 percent by weight is particularly suitable for formulations such as gear oils. Usually, the lead tallate is handled in manufacture in the form of concentrates in aromatic rich oils. Also the finished extreme pressure lubricating compositions ordinarily contain other compatible additives and components. For example, the oil may contain a chlorine containing E. P. additive, a pour depressant, a viscosity index improver, a detergent such as an alkaline earth metal sulfonate, an anti-foam agent or the like. Also, in blending extreme pressure type lubricating oils for optimum load bearing capacity, it is desirable to provide a lead to sulfur ratio of about 3:1. This may be conveniently done by incorporating a small amount of an additional lead soap such as lead naphthenate, lead oleate or lead fish oil soap. In imparting extreme pressure lubricating properties to grease composition, it is advantageous to promote the activity of the lead sulfurized tallate by the use of a small amount of an organic polysulfide as is more fully described in co-pending application S. N. 471,878, filed November 29, 1954, now Patent No. 2,790,770. The mineral oil base may be thickened to grease consistency by the usual thickening agents such as metal soaps; e. g., lithium-12-hydroxy steara-te and calcium stearate, inorganic agents of the amine coated silica types and the like.

In an example illustrating the preparation of lead sulfurized tall oil, distilled tall oil (Indusoil) was heatedv at 330 F. with 10 percent of its weight of sulfur until a copper strip of 2-3 was obtained on heating at 250 F. for one hour. This required about 12 hours. The product contained about 9 percent of sulfur and had an acidity of mg. KOH/ gm.

The lead soap was prepared by mixing 200 gms. of sulfurized tall oil, 10 ml. of butyl Cellosolve and 150 cc. of hot water by eflicient stirring while warming to F. 67 grams of lead oxide were then gradually added. The reaction was considered complete when the lead oxide had disappeared 3 to 4 hours). The water was drained and the product blown dry with air.

The lead sulfurized tall oil prepared by the above procedure was tested at a concentration of 10 percent in a lubricating oil fraction derived from a Winkler crude having a viscosity of 600 SSU at 100 F. Lead naphthenate (commercial, 30 percent), in the amount of 3 percent was added to boost the lead to sulfur ratio. The oil was blackened by the addition of a small amount of a 50:50 blend of lubricating the test oil follow:

- Analysis and inspection:

Lead percent 2.80 Sulfur do 1.13 Benzene insolubles do.. 0.12 Pentane insolubles do 0.79 Viscosity:

At 100 F. SSU 17755 At 210 F SSU- 113.7 Viscosity index 85.0 API 17.0 Evaluation:

Timken test lbs 50-55 Aging test, 96 hours at 250 F. Normal Timken test after aging lbs 50-55 When one quart samples of oils prepared by the addition of lead sulfurized tall oil in a concentration of 18 weight percent to a Mid-Continent solvent extracted lubricating oil were stored for one week at 7080 F., sediment amounting to 15 volume percent was observed to have formed. The sedimentation was reduced to nil under the, same conditions by replacing about 50% or 4 more of the Mid-Continent oil with a phenol extract from an SAE-S motor oil for example.

I claim:

An extreme pressure'lubricant consisting essentially of a viscous mineral oil base, about 10 to 15 weight percent of lead sulfurized tall oil prepared by heating tall oil with about 10 percent of its Weight of sulfur for obtaining sulfurized tall oil and then heating about 3 parts by weight of the sulfurized tall oil with about 1 part by weight of lead oxide in the presence of an aqueous medium to obtain said lead sulfurized tall oil, said extreme pressure lubricant also containing an aromaticsrich lubricating oil extract in a small but sufiicien-t amount to solubilize the lead sulfurized tall oil in said mineral oil base, a small amount of asphalt having a softening point of about 160 F., and about 3 weight percent lead naphthenate.

References Cited in the file of this patent UNITED STATES PATENTS 2,233,203 Flaxman Feb. 25, 1941 2,252,087 McNab Aug. 12, 1941 2,257,750 Lincoln Oct. 7, 1941 2,576,031 Morway Nov. 20, 1951 2,666,744 Dixon Jan. '19, 1954 2,726,209 Fainman Dec.'-6,' 1955 OTHER REFERENCES Scientific Lubrication, September 1949, pages 7, 8, 11 and 14. 

